Usage:
Hornbrook Formation (CA*,OR*)
Subunits:
(alphabetical): Blue Gulch Mudstone Member (CA*,OR*), Ditch Creek Siltstone Member (CA*,OR*), Klamath River Conglomerate Member (CA*,OR*), Osburger Gulch Sandstone Member (CA*,OR*), Rocky Gulch Sandstone Member (CA*,OR*).
Geologic age:
Cretaceous (Albian to Maastrichtian)*
Type section, locality, area and/or origin of name:
Type section (composite): NE/4 SE/4 sec. 32 to SE/4 SE/4 sec. 29, T. 47 N., R. 6 W., NW/4 NW/4 sec. 29 to middle SW/4 sec. 20, T. 47 N., R. 6 W., SW/4 sec. 20 to SE/4 SW/4 sec. 17, T. 47 N., R. 6 W., Hornbrook 15-min quadrangle, Siskiyou Co., CA (Peck and others, 1956).
AAPG geologic province:
Klamath Mountains province*
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).